Help Desk card should not require any specific license to work
the new help desk card requires an exchange o365 licenses/mailbox to be visible to a user. Not everyone uses exchange and no specific service should be required for this to work. It should just work across all services and features.
Miguel A. Tena commented
Completely agree with Sean, this should just be part of the service, you are paying for the license, so it should matter if your email is in the cloud or not. Many customers will remain hybrid for a long time and Microsoft should continue providing feature parity for cloud only and hybrid customers.